NEED HELP WITH MY NEOVIBE !!!!!

[mdh]

For what it's worth, if you live in the U.S. and have a Radio Shack nearby, it's likely that their pack of 15 NPN transistors (Catalog #: 276-1617) would work out fine for you.  They generally have hfe around 250 (may be a little low for the LFO from what I hear), and will most likely have the same pinout indicated in R.G.'s layout (apparently the opposite of what you have).  Might help you fill in the gaps if you can't salvage all of the original transistors, but be sure to pay attention to pinout!

Also, if your brother's meter has a transistor gain tester, you can use that to verify pinout.  Good luck!

[Zedmin_fx]

Ok, I went out to radio shack and purchased their  pack of  15 NPN transistors, 2n222. Followed the pinout and after removing the BC548c transistors, i soldered the new version in place. VIOLA! I now have a fully functional Neovibe! The unit sounds pretty sweet! all that is left is to build the bulb housing and......... lett-er-rip. Before i go forward with that, i would like to  solve one more problem i am facing:

I notice distortion or "crackling" on the low E and sometimes on the A string. is this part of the original design and and therefore part of the neo (staying true to the "clone" concept), or is it extra noise/gain from the  different transistors? Is it possible  a component may be faulty/wrong value, etc?   If it is "part" of the univibe sound, do you know of any mods to help clean it up?

[mdh]

Excellent! I'm glad that worked out for you.  My build has some distortion, too, probably more than what you describe, but I haven't posted on it yet, because I haven't really had a chance to take a look at it.  One thing you could try is going through the audio path with an audio probe (basically just half a guitar cable plugged into an amp on one end, and with a capacitor on the other to block DC; there's info in the wiki under "debugging" if this isn't a clear enough description), and see if you can find where the noise appears.  That will tell you where to concentrate.  This problem has definitely been described in other threads, but I'm not sure if I remember a definitive answer.

[rhdwave]

I would add that my neovibe also has distortion if it's loud enough.  Seems to depend on the level of the signal.  Was just playing it tonight with my band and actually got a complement on the sound...so props again to the great R.G.!!!  The distortion actually gives the vibe another dimension...it's not full on rat or dist plus but more of a ripple on the low strings as was just said.  I have grown to like it.  Sorry, i'm not sure if this was the intended design as you have asked, just adding my observations...

[george]

also, would it be at all profitable to switch the 1uf electrolytic caps to ordinary metal film? not only  do i want a univibe, but i  want to make sure it offers a transparent, high fidelity-type tone... will this do much for the overall tone of the pedal or is it just hype?

you're more likely to get a clearer tone by putting a buffer on the input - the neovibe has a low input impedance which sucks tone (or adds vintage vibe depending on your outlook). 

I don't think changing electros to metal film would buy you much except hassle because the metal film ones would be a lot bigger.

A source follower FET buffer on the input would do the trick (R.G. can help you with this one)

[Auke Haarsma]

Good you got it fixed!

I didn't notice any distortion on my Neovibe.

[Zedmin_fx]

OK Well my uni-vibe worked great, I love it!!! Well I brought it home from my brothers, got home and a few of the wires came off. O-boy here we go, so I put them back where they go and went to se if it worked( it didnt) the bulb lights up but WONT PULSE. So I put it into the box that I bought for it  and it still wont work. Is it bc I dont have my brothers 18vdc adapter or is something wrong?? Help

[mdh]

Well I brought it home from my brothers, got home and a few of the wires came off. O-boy here we go, so I put them back where they go and went to se if it worked( it didnt) the bulb lights up but WONT PULSE.

Are you absolutely positive that you put them back where they go?  Can you double, triple, quadruple check that?  It's so very common to think that everything is wired correctly, but if it isn't working, it probably isn't wired correctly.

Is it bc I dont have my brothers 18vdc adapter or is something wrong?? Help

Can you tell us what power supply you *are* using?  There's not much to go on here.

Edit: fixed bad quote tags!

[Zedmin_fx]

yea I am sorry I was late for work. My brothers power supply is from Jim Dunlop I am not sure the model but its from his dc brick. Currently I have a 18 vac that I used last night when it didnt work.I just bought a electroharmonix 18vdc from a store online (dont have it yet).So anyway I dont know what the problem is. To bad its a holiday and my brother cant come over to noodle with it thats just my luck.

[mdh]

Well, I think in theory the 18VAC supply should be fine, provided that the power supply portion of the board is wired correctly.  You should check the voltages on the input and output pins of the voltage regulator.  If you still only have access to a multimeter at your brother's place, you should get one of your own.  It doesn't have to be anything particularly fancy -- you should be able to find a meter in the $10-40 range that will be perfectly sufficient.  While you're at it, check the voltages on the lamp driver transistor pins and in the LFO.

I still think it's more likely that there's a wiring problem, given that the last thing that happened was that some wires came off and you reattached them (somewhere, and quite possibly not where they go).

[Zedmin_fx]

OK so by power supply portion you mean terminals (k,L) right? I will go double check the wiring in a second. And the wires that came off were on the volume control just the middle one, and on terminal a1 going to the stomp switch. Hmm maybe thats why the stomp switch didn't seem to affect the bulb?? everything Else works fine(to my knowledge). Also while I am here Do you think it might be possible to make a foot control for this thing? I was thinking that if I took the speed control and put it in a crybaby shell it might work that would be sweet.

[mdh]

OK so by power supply portion you mean terminals (k,L) right?

I mean that whole portion of the board -- the bridge rectifier, filter caps and voltage regulator, and of course the power jack itself.

I will go double check the wiring in a second. And the wires that came off were on the volume control just the middle one, and on terminal a1 going to the stomp switch. Hmm maybe thats why the stomp switch didn't seem to affect the bulb??

Hmm, I can't see any obvious reason why that would affect the LFO.  Any chance something went wrong with the depth pot?  Maybe transistor voltages (LFO and lamp driver) would be useful.  More later... late for a movie, gotta run!

[Zedmin_fx]

Why would I have to check all of that ( It worked fine for a week). OK I will check out the depth pot and see if I can get the voltages later. Also about the stomp switch ( when I plug in my power source the bulb lights up, If I hit the stomp it should start to pulse right? it doesnt) I have an 18vdc adapter but when I plug it in the bulb is really dim, yes i fiddled with the trim pot. thats why I thought it was not having the dunlop power supply.

[R.G.]

Why would I have to check all of that ( It worked fine for a week). OK I will check out the depth pot and see if I can get the voltages later. Also about the stomp switch ( when I plug in my power source the bulb lights up, If I hit the stomp it should start to pulse right? it doesnt) I have an 18vdc adapter but when I plug it in the bulb is really dim, yes i fiddled with the trim pot. thats why I thought it was not having the dunlop power supply.

Sigh...

The reason you check all that is not that the circuit has changed. It's because checking the voltages is like a doctor asking a patient where it hurts.

[Zedmin_fx]

OK I am back with the voltages. My in-put is 18.3vdc

Q1
c-e   1.1
b-e   .4
b-c   .2


Q2
c-e   3.6
b-e   .5
b-c   2.7

Q3
c-e   6.3
b-e   .6
b-c   5.1


Q4
c-e   7.2
b-e   .4
b-c   8.8

Q5
c-e   7.6
b-e   .5
b-c   4.8

Q6
c-e   6.8
b-e   .4
b-c   8.9

Q7
c-e   7.4
b-e   .5
b-c   4.3

Q8
c-e   7.2
b-e   .4
b-c   8.1

Q9
c-e   7.5
b-e   .6
b-c   4.8

Q10
c-e   9.3
b-e   .5
b-c   7.8

Q11
c-e   12.9
b-e   .5
b-c   6.6

Q12
c-e   13.7
b-e   .7
b-c   12.9

Q13
c-e   12.8
b-e   .6
b-c    11.7


      I used a different adapter from before. the new adapter has 18vdc putput and reverse polarity also this adapter has a grounded 110volts primary coil. I noticed when initially energized a puff of smoke coming from the bridge rectifier area. I have 18.3v input  and 17.6volts out of the rectifier. I now know the adapter is reverse polarity for this circut and i also wonder if the grounded primary coil has anything to do with it ( is there any such thing as a 3 pole ( hot neutral ground) secondary coil) any help would be greatly appreciated thanks.         

[mdh]

I used a different adapter from before. the new adapter has 18vdc putput and reverse polarity also this adapter has a grounded 110volts primary coil. I noticed when initially energized a puff of smoke coming from the bridge rectifier area. I have 18.3v input  and 17.6volts out of the rectifier. I now know the adapter is reverse polarity for this circut and i also wonder if the grounded primary coil has anything to do with it ( is there any such thing as a 3 pole ( hot neutral ground) secondary coil) any help would be greatly appreciated thanks.

Generally speaking, smoke is a bad sign!  Can you establish which component the smoke came from?  Photographic evidence may be helpful.  I'm wondering if maybe you grounded your power jack or the power supply itself?  If you followed the instructions in the layout (in particular, where it says, "DO NOT GROUND EITHER WIRE!!! DO NOT LET POWER JACK TOUCH CHASSIS!"), the polarity of the voltage input to the board shouldn't matter, because the bridge rectifier provides reverse voltage protection, as long as the input voltages are *not* referenced to the circuit ground.  Maybe I'm giving you a bum steer here, but I think it would be unwise to ignore a puff of smoke from the power supply... that's priority one!

[Zedmin_fx]

Well the smoke puff i saw was about 2 inches long I immediately took out the power when i saw that happen. It came when i put a wire into terminal j.so I think if i am remembering correctly it came from that terminal. Do you think this thing is junk and I have to start from scratch or can i save it?

[mdh]

My best guess is that you might have put the whole supply voltage across one of the diodes in the bridge rectifier, which will let the blue smoke out of that diode, so to speak.  I believe this could happen if you connected the ground terminal of the voltage coming in  at pads K/J with the circuit ground.  But, if you removed power immediately, it's possible that you just damaged the bridge rectifier (though I suppose it's possible that the 1000uF filter caps were damaged, as well, but I'd have to think about that).  So if I were you, I would replace the bridge rectifier, make sure I understand how to properly wire up the power supply, and give it another shot.  It's very important that you follow the instructions about not connecting pads K or J to ground, and not letting the power jack make electrical contact with the chassis (and hence, circuit ground).

[finkfloyd]

I reckon you have put the 7815 volatge regulator in the wrong way round, if you did do this, the voltage regulator would get very hot and smoke, i have done this before, as I had some which where non standard pinouts.

so if i were you try replacing the voltage regulator and make sure it faces the other way, before you do this , if you have this socketed, verify that this is the component smoking, if it is replace and put in the other way round

[mdh]

I'm guessing that the regulator isn't the problem, because his board previously worked with a different power supply, and the smoke was observed near pad J, which is right next to one of the bridge rectifier pins.  That's my reasoning, anyway.